It is commonly known that under the conditions of industrial machining of workpieces, the number of the instances of starting the pump for a machining operation and stopping it for either workpiece replacement or some other interoperation interval can be as great as 6 to 10 times per minute, which is a highly unwanted operating duty for a pump, eventually resulting in untimely wear and even complete failure of the latter.
A hitherto known arrangement for electrochemical machining of workpieces, providing for a normal operating duty of the pump, comprises an electrode tool adapted to be fed during a machining operation toward the workpiece supported on a work table and to be retracted from this workpiece for an inter-operation interval, a pump mounted in a common line upstream of the point of branching off of a working line for supplying the working fluid from a tank to the workpiece being machined and of a bypass line for circulation of the working fluid through an intermediate vessel into the fluid tank, and also line switching control means coupled with the control elements of individual valves mounted in the respective ones of the lines and adapted to open, now, the flow through the working line as the electrode tool is being fed toward the workpiece, then, the flow through the bypass line during an inter-operation interval.
The line switching control means in the known arrangement comprises two individual electric actuators operatively connected each with the control element of the respective valve and electrically coupled to an electric circuit setting out the operating cycle diagram of the arrangement.
As the electrode tool is fed toward the workpiece, the aforementioned electronic circuit sends a command signal to energize the individual actuator coupled with the valve mounted in the working line, and another command signal to deenergize the individual actuator coupled with the valve in the bypass line. In this way the flow through the working line is opened, and the flow through the bypass line is arrested.
For the duration of an inter-operation interval, in a similar way the bypass line is opened, and the working line is closed.
Every switching operation in the aforementioned arrangement is dependable on a relatively complicated electronic and electric equipment which, however, is not as reliable as mechanical connections.
Besides, the known arrangement inclues individual means for adjusting the rate of flow of the working fluid, which further complicates both the structure and performance of the arrangement.